Very interesting topic! In Alberta, Canada, I have not experienced a limit or refusal of credit when buying gas. All credit and debit cards here have chips and pins so maybe they are more secure?
I am interested in the question of who pays for credit card fees, which I think amount to enormous revenue for banks and some pretty good kickbacks to cardholders. A farmer here brags that when he buys $100k of fertilizer on his Royal Bank credit card, he gets enough points to go first class to Europe, including hotels. I expect the fees to merchants end up being paid for by customers somehow. Here there are no fees charged to customers paying by credit card, even when they use 5% kickback cards, so all customers must be helping pay for the farmer's holiday through increased prices.
Some gas stations offer bonus points if you use a particular credit card. For example the Superstore gas bar offers 7 cents per Liter in grocery credits when paying with a Presidents Choice card. I speculate that this is the amount the store saves in fees it would have to pay if the customer used a different card.